Halo-substitution of unsaturated organic compounds



Patented Apr. 7, 1942 UNITED STATES PATENT OFFICE HALO-SUBSTITUTION F UNSATURATED ORGANIC COMPOUNDS Frederick F. Rust and William E. Vaughan,

Berkeley, Calif., asslgnors to Shell Development Company, San Francisco, Calif., a corporation of Delaware No Drawing. Application September 5,

Serial N0. 293,486

14 Claims.

halogenated unsaturated hydrocarbons which contain an olefinic linkage between two nontertiary carbon atoms of aliphatic character.

The process is essentially one of halo-substitution at elevated temperatures, and is executed by subjecting an unsaturated organic compound of the above-defined and hereinafter described class to a halogenation reaction, in the presence of a catalyst described hereinbelow, at an elevated temperature which is, however, below that which is necessary for effecting substantial halosubstitution under ordinary thermal, non-catalytic operating conditions.

The halo-substitution of unsaturated organic compounds of a tertiary character, such as tertiary olefins and halo-substitution products thereof, is not strictly within the scope of this invention dueto the normal tendency of these olefins to undergo halo-substitution, to the exclusion of the halogen addition reaction, at ordinary and even reduced temperatures. It is to be noted, however, that this low temperature halosubstitution of unsaturated organic compounds of a tertiary character, is into allylic position. Thus, when 2-methyl butene-Z is chlorinated at abou room temperature, the reaction product consists of l-chlor Z-methyl butene-2 and/or 2- methyl 3-chlor butene-l (the latter being obain d bv an allvlic shift of the double bond), On the other hand, high temperature halogenation of such tertiary olefins gives rise to prodstitution under thermal, non-catalytic halogenation. Otherwise stated, for any given temperature (above a certain minimum mentioned below), the presence of the catalyst increases the yield of products of halo-substitution and inhibits halogen addition. Therefore, the present invention may be applied to those cases of halo-substitution of unsaturated organic compounds of a nets in which the halo-substitution is not only process of the present invention is one of halosubstitution at elevated temperatures in the presence of a catalyst to be described hereinbelow, this catalyst promoting halo-substitution at relatively lower temperatures than those necessary for obtaining substantial amounts of halo-subtertiary character, wherein it is desired to obtain products of halo-substitution which would be derived by the high temperature non-catalytic halogenation, the halogenation of such tertiary unsaturated organic compounds according to the present invention lowering the operating temperature and simultaneously increasing the yield of' products of halo-substitution in which the halogen atom is attached to carbon atoms which are in turn attached to primary and/ or secondary carbon atoms.

In the case of the unsaturated organic compounds of primary and secondary character, such as ethylene, secondary olefins and products of their partial halo-substitution, the reaction of halo-substitution does not occur at all at the ordinary and reduced temperatures. In fact, at such ordinary temperatures and even at considerably elevated temperatures, the normal halogenation reaction, when effected on the primary and secondary unsaturated organic compounds, is that of halogen addition in which the halogen adds to the olefinic linkage to saturate the same and yield a saturated polyhalide. The only halogen substitution reaction which takes place under such operating conditions is the so-called induced substitution, which is eiiected by haloaddition to an unsaturated compound which then initiates halo-substitution into a saturated compound such as a saturated dihalide, previously formed by the halogen addition reaction, or a concurrently present saturated hydrocarbon.

It was previously found that unsaturated organic compounds of primary and secondary character may be halogenated, via substitution, to the substantial exclusion of the formation of products of halogen addition, if the halogenation r action is realized at elevated temperatures of above about 200 C. but below the temperature at which substantial degradation such as crackin splitting out of a hydrogen halide, polymerization, etc., of the organic'reactant and/or product occurs. The preferred temperature range for such halo-substitution of the unsaturated organic compounds of a primary and secondary character will depend on the specific compound to be subjected to the'halo-substitution reaction. Thus, a

preferred temperature range for the production of vinyl chloride by the thermal chlorination, via substitution, of ethylene is from 300 C. to 500 C., the conversion being substantially quantitative at about 400 C., the reaction product being also substantially free of either dichloroethane or trichloroethane. On the other hand, in order to chlorinate propylene to allyl chloride, the preferred temperature range is from 350 C. to about 675 C., while a preferred temperature range for the allylic halo-substitution of the normal butylenes is from about 200 C. to about 400 C. Generally, it may be stated that substantially complete conversion is usually obtainable at the'higher limits of the specified preferred ranges, while near the lower limits of such ranges, i. e. at around 200 C. to 250 0., although halo-substitution occurs in preference to halogen addition, the products of reaction, nevertheless, contain appreciable percentages of such halo-addition products The above-outlined process for the thermal halo-substitution of unsaturated organic compounds of a primary and secondary character is described and claimed in U. S. Patents Nos. 2,130,084 and 2,167,927.": The first of these two patents covers the high temperature halogenation, via allylic halo-substitution, of unsaturated organic compounds of secondary character, such as unsaturated hydrocarbons containing an olefinic linkage between two non-tertiary carbon atoms of aliphatic character at least one of which is of secondary character; while Patent No. 2,167,927 is directed to a process for the direct halogenation, via substitution, of ethylene and its halo-substitution products containing at least one hydrogen atom.

It has now been discovered that the unsaturated organic compounds of the above-defined and hereinafter described class may be eflectively subjected to halogenation, via substitution, at substantially lower temperatures than those heretofore necessary for substantial halosubstitution, and that the products of reaction obtained are substantially free of products of halogen addition.

It has been further discovered that the presence of small and definite quantities or percentages of oxygen, when operating at the same elevated temperatures, will inhibit this halogen addition and simultaneously promote substantially quantitative halogenation via substitution.

This discovery was quite unexpected since it was considered that the presence of oxygen inhibits halogenation reactions. Thus, Pease and Walz (Journal Am. Chem. Soc vol. 53, page 382) have stated that below about 375 C. oxygen suppresses the thermal chlorination of methane, whereas above that temperature the rate of uns'uppressed reaction is so high that the presence of 5% oxygen has no measurable efiect. Also, Luther and Goldberg, in their article in Z. physik Chem. vol. 56, p. 43, describe the inhibition of chlorine substitution into benzene, toluene, xylene and acetic acid, and conclude that this is a typical phenomenon.

As stated above, the present invention is primarily directed to the halo-substitution of unsaturated organic compounds or primary and secgreatly inhibit or even prevent any reaction thereof with the halogen. Thus, propane was subjected to chlorination at temperatures of between about 31'7" and 329 0., both in the presence and absence of small quantities of oxygen in the order of 1% by volume of the gaseous mixture. Whereas the propane in the absence of the oxygen reacted almost completely with the chlorine, the presence of the small quantity of oxygen greatly inhibited the chlor-substitution oxygen promotes such halo-=substitution at tem=' peratures below those described as necessary for the substantially quantitative halo-substitution, and that such oxygen, besides promoting the halo-substitution reaction, apparently inhibits the halo-addition reaction so that the resultant products. although obtained at temperatures below those necessary for the substantially quantitative halo-substitution according to the teachings of the aforesaid patents, are substantially free of saturated halides. It was also discovered that the presence of the small and limited percentages of oxygen greatly increases the yield of products of halo-substitution and, at the same time, inhibitsthe formation of halogen addition products, as compared to the results obtained when the reaction between the compounds de-' scribed herein and the-halogen is effected in the absence of such oxygen, even though both reactions are carried out at the relatively high temperatures of above 300 C. In other words,

although when operating at these high tempera. 'tures, halo-substitution occurs even in the abreaction, so that only about 10% of the chlorine present was consumed. Similar inhibition of the halo-substitution reaction was noticed when oxygen was present during high temperature halogenations, via substitution, of other saturated organic compounds.

Representative unsaturated compounds of the class which may be halo-substituted according to the present invention comprise: ethylene and products of its partial halo-substitution, such as vinyl chloride, vinyl bromide, acetylene dichloride, brom=substituted vinyl chloride, and the like; secondary olefins, such as propylene, the normal butylenes (butane-1 and butane-2), the normal amylenes, secondary isoamylene, the normal hexenes the iso-hexenes of secondary character, the normal heptenes, the iso-heptenes of secondary character, and the straight and branched chain secondary octylenes, nonylenes l, 3-chlor-2-brom-propene-1, and the like, theirhomologues and analogues; and cyclic olefinic compounds of secondary character and halosubstitutiomproducts thereof, such as cyclobutene, cyclopentene, cyclohexene, cycloheptenes. cyclooctenes, and the like as well as the halosubstituted cyclic olefins. The primary and secondary olefins, the cyclic oleflns of secondary Y i-phenyl butene-2' and the like may be halogenated by halogen substitution in accordance with the process of the invention.

The maximum quantity oi oxygen which may be employed for the promotion of the halo-substitution reaction according to the present invention is rather small. Generally speaking, very small percentages of oxygen are eflective to promote the reaction and to eilect a substantial halo-substitution while, at the same time, inhibiting the halogen addition. Thus, the quantity of oxygen should preferably be less than about 2 to 3% by volume'oi the gaseous mixture subjected to halogenation. cases it is possible to employ as much as 5% oxygen, although larger throughputs of oxygen retard the halogenation reaction, unless higher temperatures are employed. In the case of the halo-substitution of ethylene and of propylene, when operating at temperatures of about 300 C., substantially quantitative halo-substitution was obtained .with oxygen concentrations of about 0.5% to 0.7% by volume.

The halo-substitution promoting effect of oxygen appears above certain temperatures which depend on a number of variables, such as type of unsaturated organic compound to be treated, type of halogen employed, presence and kind of diluent, ratios thereof, etc. Below these temperatures, the presence of oxygen, instead of catalyzing the halo-substitution reaction, inhibits and even suppresses both the halo-substitution and the halogen addition reactions. Generally, the lower temperature limit for ethylene is in the neighborhood of about 250 C. For propylene this temperature is between about 265 C. and 270 0., while that'for butene-2 is about 260 C.

The invention is illustrated by the following examples which are presented for the purpose of showing various modesof executing the process and the improved results obtainable thereby. It is to be understood, however, that these examples are merely'illustrative of the invention. and should not be considered as limiting the invention in any sense.

Example I An ethylene-chlorine mixture. in a volumetric ratio of 2:1, was first diluted with an equal part of nitrogen, and then conveyed at different temperatures and with and withoutv small percentages of oxygen, through a reaction zone at a rate of about 300 c.c./min. The results obtained in these series of runs are presented in tabulated An analysis of the above results indicates that, for the given ratios, the presence of 3% by volume of oxygen, inhibits both halogen addition and halo-substitution when the reaction was effected at 245 C. On the other hand. when eiiected at However, in some 264 C. or higher, the presence 01 the same quantity of oxygen greatly increased the total consumption of chlorine and simultaneously inhibited halogen addition, so that the reaction products consisted substantially solely of products oi halo-substitution, i. e., of vinyl chloride.

Example I! A mixture consisting of one part by volume of chlorine, 2 parts by volume of propylene and three parts by volume of nitrogen was conveyed through a reaction zone at a rate of 300 c.c./min. and subjected to elevated temperatures with and without the presence of small percentages oi oxygen. Three series of runs were made at temperatures of about 262 0., 273 C., and 286 C., respectively, each series consLsting oi a run in which no oxygen was used and one in which about 3% to 5% by volume of oxygen was added. The following results were obtained:

Total 01, 01, reacted Temperature Oxygen med by substiby addition tution Percent Percent Percent Percent None 62.1 31.0 31.1 5 0.0 0. 0 0.0 None 76. 4 45. 2 31. 2 3 90. 8 00. 8 0.0 None 83. i 55.0 28. i 3 89. 6 88. 6 l. 0

At the lower temperature of about 263 C., the addition of 5% .of oxygen to the diluted propylenechlorine mixture completely inhibited the chlorination reactions both via addition and via substitution. On the other hand, at temperatures above about 270 C., the presence of 3% by volume of oxygen was beneficial in two ways since it increased the overall consumption of the chlorine and simultaneously. inhibited the chlor-addition so that principally products of chlor-substitution were found in the obtained reaction product. It is to be noted that when the halogenation reaction is eii'ected in the absence of oxygen,- the quantity of chlorine which reacts by addition decreases with an increase in the reaction tem perature. Thus, in the above case, there was a 3.1% reduction in the quantity of chlorine reacting by addition when the temperature was raised from 272 C. to 286 C. Simultaneously, the products of chlor-substitution increased from 45.2% to 55.0% as based on the chlorine reacting via substitution. If the reaction temperature were raised sufilciently high, i. e., to about 600 C. or even higher, the products obtained would consist substantially only of unsaturated chlorides obtained by chlor-substitution. This is disclosed and claimed in the aforementioned U. S. Patent No. 2,130,084. Instead of using such elevated temperatures, the above table shows that substantially similar results may be obtained by efiecting the chlorination reaction at temperatures of below 300 C. if the reaction is effected according to the present process in the presence of small percentages of oxygen which, as stated, promotes substantially quantitative chlor-substitution while inhibiting, and even completely suppressing the chlorination by addition.

Example III Gaseous propylene and chlorine diluted with nitrogen, were reacted in a heated reactiontube 2:1, and this mixture was diluted with three volumes of nitrogen. The diluted mlxturewas then conveyed through the reaction tube at a rate of about 300 c.c./min., the reaction being effected at about 310 C. An analysis of the effluent gases showed that about 54% of the chlorine reacted with the propylene, and that 36% of the total chlorine introduced reacted by substitution.

A similar run was conducted under the same operating conditions, the reaction mixture, however, containing 1% by volume of oxygen. The total consumption of chlorine in this run was 64%, i. e. an increase of while 48% of the introduced chlorine reacted by substitution. On the other hand, when the same reaction was effected in the presence of about 2%% oxygen, the total consumption of the chlorine dropped to about 37%, and that of chlorine reacting by substitution to about 26%.

These results clearly show the advantage obtained by the use of small and controlled percentages of oxygen to promote halo-substitution, and thatthe use of excessive quantities of the oxygen inhibits both the chlorine addition and chlor-substitution reactions.

Example IV A mixture of ethylene, chlorine and nitrogen (with and without small percentages of oxygen) was conveyed through a reaction zone at a rate of about 300 c. c./min. and at atemperature of about 324 C. The proportions of the reactants and diluent were such that 25 c. c./min. of chlorine, 50 c. c./min. of ethylene, and 225 c. c./min. of nitrogen and oxygen passed through the reaction zone. The first run contained no oxygen, while the subsequent runs contained small and carefully controlled percentages of this catalyst.

The results are presented in the following table:

Chlorine reacted Oxygen by Total By substi- By additution tion Percent Percent Percent Percent None 39 14 25 88 76 13 M 91 87 4 1%; 21 6 2 13 4 I 9 The above figures clearly indicate that the presence of small percentages of oxygen increases the yield of products of chlor-substitution, while inhibiting the formation of saturated chloro-ad-' dition products. Thus, the addition of /2% by volume of oxygen, when operating under the above-outlined conditions, increased the total consumption of chlorine from 39% to about 91%,

while the quantity of chlorine reacting by ad-' A diluted ethylene-chlorine mixture was reacted under the same conditions as those described in the previous example, except for the fact that the reaction temperature was 334 C. As in the above example, a series of runs was conducted with varying percentagesof oxygen being added to the mixtures to determine the catalyzing effect of oxygen at the 334 C. temperature. The following results were obtained.

Oxygen by Chlorine reacted v0 ume of Total News By substi- By addimlxmre tution tion Percent Percent Percent Percent None 38. 5 16 22. 5 is 88.5 84 4. 5 92.5 92. 5 0 m 32 19 s 2 16 4 12 3 l3 0 12 Thus, the addition of as little as about 0.6% to 0.7% by volume of oxygen increased the chlorsubstitution from 16% to 92.5%, while the 22.5% of addition products were eliminated. Further increase in the quantity of added oxygen gradually suppressed all of the chlor-substitution, but the chlor-addition was again raised to about 12 to 13% as calculated on the percentage of chlorine reacting with the ethylene.

The optimum oxygen concentration is apparently affected only slightly by a change in the operating temperature, it being noted, however, that at the higher temperatures .there is an increased amount of unsuppressible halogen addi-' tion. Furthermore, experiments have shown that at the higher temperatures it is possible to employ somewhat greater percentages of oxygen (above the optimum amount) without materially inhibiting the halo-substitution reaction. This is particularly noticeable with unsaturated organic compounds of secondary character. Also, reaction tubes which contain materials increasing the reaction surface, apparently require slightly higher temperatures to show evidence of positive catalytic action of oxygen. In other words, as compared to an unpacked tube of the same diameter and length, a reaction vessel containing such reaction surface increasing materials, should be operated at a somewhat higher temperature to have the oxygen catalyze the halo-substitution instead of inhibitin all halogenation of the unsaturated organic compound subjected to treatment according to the process of this invention.

Although the reactions. described in the above examples were all effected with olefin-chlorine mixtures having a mol ratio of 2:1, the reaction according to the present invention may'be effected with either the halogen or the olefinic (or like) compound in excess, or with the reactants in equimolecular amounts. In general, it is preferred to employ an excess of the unsaturated organic compound of the described class because, in such case, the yieldof the desired product, based on the applied halogen, is usually better and the temperature control is facilitated. Olefinic compound to halogen mol ratios of from 2:1 to 7:1 and higher may be successfully employed. When an excess of the halogen is used, there is a greater tendency to form polyhalogenated unsaturated compounds.

The control of the production of monohalides may be effected by the use of diluents, such as nitrogen, carbon dioxide, helium, etc. The presence of such-diluent further inhibits tar and/or carbon formation.

The reaction may be eflected at any suitable pressure, although it is preferably realized in the gaseous phase at about atmospheric or moderately elevated pressures. Instead of employing a free halogen per so, such as chlorine, bromine, etc., it is possible to employ any of the known free halogen yielding substances which are capable of liberating a free halogen under the conditions existing in the reaction system.

The halo-substitution reaction is always accompanied by the formation of hydrogen halide. This hydrogen halide may cause certain undesirable side-reactions, such as the addition 01 this halide to the applied unsaturated organic compound and/or to the product of halo-substitution. In order to avoid the occurrence of these side-reactions, it may be desirable to cool and/or separate the hydrogen halide from the unsaturated organic materials substantially as soon as the mixture leaves the reactor. This may be accomplished in a variety of suitable manners. Thus, the eiiiuent material leaving the reaction zone may, for example, be contacted with a selective solvent for the hydrogen halide in a suitable scrubbing apparatus. As such solvent, reference may be made to water, which not only preferentially dissolves the hydrogen halide, but also dilutes the same, thus rendering it less active. The products of reaction may then be separated from the unreacted unsaturated hydrocarbon by -'any suitable rectification and/or extraction methods.

The invention may be executed in an intermittent or continuous manner. The space velocity or rate of passage of the reactants through the reaction zone will depend upon a number of variables, such as type of reactants, the design of the reaction chamber, temperature employed, mol ratio of the reactants, quantity of diluent, if any, type of desired products of halo-substitution, etc. In general, good results are obtained by employing the maximum flows which may be reacted in a given reactor. Thus, the rate of production withthe given equipment, is at a maximum and the time during which the reaction products are maintained at the reaction temperature is reduced to a minimum. Under such conditions the rates of iiow are faster than the rate of flame propagation, so that undesirable flashing, tarring" and/or carbon formation, are

prevented or, at least, greatly decreased.

The use of the catalyst according to the present invention also increases the rate of halo-substitution, so that, under identical operating conditions, the halo-substitution in the presence of the small percentages of oxygen requires a relatively shorter period of residence time as compared to a thermal halogenation operation without the us of a catalyst. Therefore, the present process allows greater space velocities to effect the same conversion of the treated organic compound, thus increasing the eifective capacity or throughput of any given reaction chamber.

Since the halogens and the olefmic compounds of the character described herein will react rapidly via halogen addition when brought into contact at room temperature, it is necessary, if halosubstitution to the substantial exclusion of halogent addition is desired, that the reactants be brought together, and in contact with the oxygen catalyst, at an elevated temperature so high that substantially no halogen addition can occur. Also, the temperature must be such that the oxygen acts as the halo-substitution pro- 75 moting catalyst. The above may be accomplished by separately preheating the reactants, followed by commingling at the desired temperature. In the alternative, the unsaturated organic compound may be preheated and commingled with unheated or only partially heated halogen, or the halogen may be preheated and mixed with the unheated or partially heated unsaturate to be halogenated. The oxygen employed as the catalyst may be added before, during and/or after commingling. Since the reaction is exothermic in character it is unnecessary to preheat the reactants to the optimum reaction temperature. Usually, the preheating temperature should be above about 150 C., and preferably to still higher temperatures.

The heating of the reactants may beefiected by any known means, such as furnaces, resist ance coils, etc., which may be provided on the pipes leading one or both of the reactants to the mixing and reaction zones. In order to prevent carbon formation both in the mixer and reactor, it is preferable to construct or line the interior of the mixing and/or reaction zones with substances, such as hard carbon, which are substantially inert to the action of a. heated halogen.

The oxygen employed for the purpose of catalyzing the halo-substitution reaction may be pure or be commingled with inert substances, as in th case of air.

We claim as our invention:

1. The process of chlorinating propylene via substitution, which comprises reacting propylene in the vapor phase with gaseous chlorine in the presence of oxygen in a quantity of up to 5% by volume of the gaseous mixture, and at a temperature in excess of 265 C., but below that at which substantial chlor-substitution is efiected during a thermal, non-catalytic chlorination reaction in the absence of oxygen.

2. The process of halogenating propylene via substitution, which comprises reacting propylene in the vapor phase with a gaseous halogen se lected from the group consisting of chlorine and bromine, in the presence of oxygen in a quantity of up to about 5% by volume of the gaseous mixture, and at a temperature in. excess of 265 C., but below that at which substantial halo-substitution is effected during a thermal, non-catalytic halogenation reaction.

3. The process of chlorinating ethylene via substitution, which comprises reacting ethylene in a vapor phase with gaseous chlorine in the presence of oxygen in a quantity of up to 5% by volume of the gaseous mixture, and at a temperature of above 250 C., but below that at which substantial chlor-substitution is effected during a thermal, non-catalytic chlorination reaction, whereby th ethylene is chlorinated by substitution while chlorine addition is substantially inhibited:

4. The process of halogenating ethylene via substitution, which comprises reacting ethylene in the vapor phase with a gaseous halogen selected from the group consisting of chlorine and bromine, in the presence of oxygen in a quantity of up to about 5% by volume of the gaseous mixture, and at a temperature of above 250 C., but below that at which substantial halo-substitution is eiiected during a thermal non-catalytic halogenation reaction whereby the ethylene is halogenated by substitution while halogen addition is substantially inhibited.

5. The process of predominantly chlorinating, via substitution, an unsaturated organic compound of the class consisting of unsaturated hydrocarbons and halo-substituted unsaturated hydrocarbons containing an oleflnlc linkage between two non-tertiary carbon atoms, which comprises subjecting said unsaturated organic compound in the vapor phase to the action 01 gaseous chlorine in the presence 01' oxygen in a quantity up to by volume of the gaseous mixture, and at an elevated temperature of above 250 0., but below that at which substantial older-substitu- *tion is favored during a thermal, non-catalytic halogenation, whereby substantial chlor-substitution of the unsaturated organic compound is effected, while inhibiting chlorine addition.

6. The process according to claim 5 wherein the quantity of oxygen is between about and 3% by volume of the gaseous mixture subjected to the chlor-substitution reaction. I

7. The process of predominantly chlorinating via substitution, an unsaturated organic compound of the class consisting of unsaturated hydrocarbons and halo-substituted unsaturated hydrocarbons containing an olefinic linkage between two non-tertiary carbon atoms, which comprises subjecting said unsaturated organic compound in the vapor phase and at a temperature of above 250 C., but below the temperature at which substantial decomposition occurs, to the action of gaseous chlorine in the presence of oxygen in a quantity of up to 5%, said oxygen catalyzing the reaction and effecting substantial chlor-substitution of the unsaturated organic compound, while inhibiting chlorine addition.

8, The rocess according to claim 7, wherein the quantity of oxygen is between about and 3% by volume of the gaseous mixturesub jected'to the chlor-substitution reaction.

9. The process of predominantly halogenating, via substitution, an unsaturated organic compound of the class consisting of unsaturated hydrocarbons and halo-substituted unsaturated hydrocarbons containing an olefinic linkage between two non-tertiary carbon atoms, which comprises commingling said unsaturated organic compound with a halogen selected from the group consisting of chlorine and bromine, an inert diluent, and oxygen in a quantity of up to about 5% by volume of the gaseous mixture, and executing the halo-substitution reaction at a temperature of above 250 C. but below that at which substantial halo-substitution is efiected by thermal, non-catalytic halogenation.

10. Th process of predominantly halogenat-' ing, via substitution, an unsaturated organic compound of the class consisting of unsaturated hydrocarbons and halo-substituted unsaturated hydrocarbons containing an oleflnic linkage between two non-tertiary carbon atoms, which comprises subjecting said unsaturated organic compound in the vapor phase to a reaction with a gaseous halogen selected from the group consisting oi chlorine andbromine, in the presence 01' oxygen in a quantity of between about and 3% by volume of the gaseous mixture, and at a temperature of above 250 C., but below that at which substantial halo-substitution is effected by thermal, non-catalytic halogenation, whereby substantial halo-substitution is efiected to the substantial inhibition of halogen addition.

11. The process of predominantly halogenating, via substitution, an unsaturated organic compound of the class consisting of unsaturated hydrocarbons and halo-substituted unsaturated hydrocarbons containing an oleflnic linkage betw' two nou -tertiary carbon atoms, which comprises subjecting said unsaturated organic compound in the vapor phase to a reaction with a gaseous halogen selected from the group consisting of chlorine and bromine, at an elevated temperature of above 250 C., but below the temperature at which substantial decomposition occurs, and in the presence of oxygen in a quantity of up to 5%, thereby obtaining substantial exclusion of halogen addition. a

12. Th process of predominantly halogenating, via substitution, an unsaturated organic compound of the class consisting of unsaturated hydrocarbons and halo-substituted unsaturated hydrocarbons having an olefinic linkage between two non-tertiary carbon atoms, which comprises subjecting said unsaturated compound to the action of a halogen selected from the group consisting of chlorine and bromine, and efiecting said reaction in the presence of oxygen in aquantity of up to about 5% by volume of the reactants and at a temperature in excess of 250 C., but below that at which substantial halo-substitution is efiected during a thermal, non-catalytic halogenation reaction whereby material halo-substitution is effected as compared to the halosubstitutlon obtainable at such temperature by a thermal, non-catalytic halogenation.

13. Th process according to claim l2,-wherein the oxygen is employed in a quantity of between about 543% and 3% by volume of the reactants.

14. The process according to claim 11, wherein the oxygen is employed in a quantity of between about Va% and 3% by volume 0! the reactants.

FREDERICK F. RUST. WILLIAM E. VAUGHAN. 

